1. Field of the Invention
The present invention relates to a hologram-including medium which is a medium on which at least two items of identification information are recorded, and in which one of the two items of identification information is holographic identification information, and relates to a hologram-including medium producing apparatus and an information determination method.
2. Description of the Related Art
Holograms capable of presenting stereoscopic images are used for authentication of credit cards, identification cards, and the like. At present, embossed holograms which record information using surface unevenness of an interference film are widely used. However, the embossed holograms have a problem in that they are easy to counterfeit. In contrast, volume holograms which record information using differences in the refractive indices in an interference film are very difficult to counterfeit. This is because a sophisticated technique is used to produce a recording image, and also such a recording material is difficult to obtain.
There are two production methods for a volume hologram, namely, a real-scene hologram and a holographic stereogram. To produce a real-scene hologram, a laser is irradiated onto an object. In contrast, a holographic stereogram is recorded based on parallax images from a number of viewpoints. The production process of a volume holographic stereogram generally includes a content production step which includes an image acquisition step, an image editing step, and other processing of the acquired images, a hologram master producing step, and a replication (mass production) step. The images are acquired by image capturing or computer graphics. Each of a plurality of images acquired in the image editing step is converted to a strip-shaped image, for example, by a cylindrical lens. The master is produced by sequentially recording interference fringes between the object beam and the reference beam of the image on a hologram recording medium as strip-shaped elementary holograms. The hologram is replicated (mass-produced) by contact printing using the master. That is, the hologram recording medium is brought into contact with the master, followed by irradiation of a laser beam, whereby the hologram is replicated.
As described above, a volume hologram itself can be replicated by bringing an unexposed hologram recording material into close contact with the hologram and irradiating a laser having a wavelength close to the recording wavelength to the recording medium. In many cases, for mass production of holograms, the same holograms are used for a number of products.
Therefore, it is desirable to provide a higher level of authentication features and anti-counterfeiting features to the hologram itself so that individual holograms themselves can be differentiated from each other. In this case, it is desirable that the identification information assigned to the holograms in order to make the individual holograms distinguishable is readable with a machine or the naked eye. Moreover, considering the use of holograms, it is desirable to provide a higher level of authentication features and anti-counterfeiting features to hologram products coupled with the hologram, thus further improving security.
JP-T-2005-535469 discloses a technique that makes counterfeiting of hologram products more difficult. According to this technique, codes are recorded or printed on a volume hologram and a document to be protected, and the hologram is attached to a document on which the same code as that recorded on the hologram is printed. In this way, a document which is reliably protected by the hologram is produced.